I wanted to clear up the kidney cyst issue and agree with Dr. Williams that polycystic kidney disease is different than cystic kidneys. Polycystic kidney disease we have only seen in ferrets under 1 year of age and it has involved both kidneys extensively and is not a good prognosis. It is indeed rare, but Dr. Judy Bell at Marshall Farms has told me that she sees it now and again as a kit disease. The cause is unknown. Out of about 5000 ferrets that I have seen we have seen maybe 4 cases. Cystic kidneys on the other hand are relatively common and as Dr. Williams pointed out is usually a benign condition. I see it usually in older animals over three, but apparently it can be in any age (although I have not seen it in younger animals). I would guess that about 10% of the ferrets we see will develop a cyst in one or more kidneys without a problem. All the cases of hydronephrosis we have seen (where the ureter of the kidney is nonfunctional or blocked) have been in ferrets under 18 months of age and all in females associated with a problem at the time of a spay. I was most interested to learn that Dr. Williams had seen one also caused by a urinary infection. Ferrets can also develp bladder stones and kidney stones, but I have not yet seen a blocked ureter and consequently hydronephrosis because of it. Thanks for the extra info Dr. Williams! Last note... due to some personal committments and business schedule, I will not be easily available for questions on this network for the next two weeks. I know you will not need my with Dr. Williams around. I will check in every so often and hope to be back more regularly in a couple of weeks.....happy ferreting! Susan Brown, D.V.M. [Posted in FML issue 0810]